Effect of III‐nitride polarization on V_OC in p–i–n and MQW solar cells

Abstract

We performed detailed studies of the effect of polarization on III‐nitride solar cells. Spontaneous and piezoelectric polarizations were assessed to determine their impacts upon the open circuit voltages (VOC) in p–i(InGaN)–n and multi‐quantum well (MQW) solar cells. We found that the spontaneous polarization in Ga‐polar p–i–n solar cells strongly modifies energy band structures and corresponding electric fields in a way that degrades VOC compared to non‐polar p–i–n structures. In contrast, we found that piezoelectric polarization in Ga‐polar MQW structures does not have a large influence on VOC compared to non‐polar MQW structures. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Improved Photovoltaic Effects of a Vertical-Type InGaN/GaN Multiple Quantum Well Solar Cell

“…22,23) Furthermore, our recent studies indicate that polarization effects in p-i-n structures adversely reduce internal electrical fields inside intrinsic InGaN layers, leading to a lower open circuit voltage (V OC ) and short circuit current (J SC ) compared to MQW solar cells. 24) Hence, InGaN/GaN MQW solar cells can be an alternative approach for improving energy conversion efficiencies with higher indium composition. [15][16][17] However, even with MQW solar cell structures, the overall InGaN thickness is limited to less than 50 nm, which is far from optimal light harvesting for high efficiency solar cells.…”

Structural and optical study of core–shell InGaN layers of nanorod arrays with multiple stacks of InGaN/GaN superlattices for absorption of longer solar spectrum

“…First, we consider the energy band alignment of p-i-n structures since the indium composition can critically affect the electric field in an i-InGaN layer. 33) The energy band simulation was implemented using SiLENSea commercial software for calculating the semiconductor features of nitride devices. 34) Figure 1(a) shows the energy band structures for Ga-polar p-i-n solar cells at zero bias with indium compositions of 5, 15, and 25%.…”

“…1(a), we can expect photovoltaic generation only at the two InGaN=GaN interfaces for high-indium Ga-polar solar cells but not inside the i-InGaN layer. 33) However, for the nonpolar solar cells, a large number of excitons can be generated in the i-InGaN region despite a slight reduction of V oc . Therefore, we expect that nonpolar InGaN-based solar cells with a core-shell nanostructure can achieve high efficiency by combining them with interlayers underneath the i-InGaN layer.…”

Investigation of properties of InGaN-based vertical-type solar cells with emission wavelengths in ultraviolet-blue-green regions

“…15 Accordingly, to maintain the high In composition and high crystal quality, several groups adopted InGaN/GaN MQW solar cells, 16,17 though these solar cells still have a low Jsc and FF. Also, other groups recently reported the carrier transport in InGaN/GaN solar cells by barrier thickness and temperature.…”